Metastatic olfactory neuroblastoma: A small round blue cell puzzle on fine‐needle aspiration cytology

Abstract

Small round blue cell tumors (SRBCTs) are a heterogeneous group of malignant neoplasms that can be challenging to distinguish on fine-needle aspiration (FNA) cytology. Ancillary tests as well as clinico-radiological correlation are often required to make an accurate diagnosis. FNA is a low-cost, low-infrastructure test, making it a coveted diagnostic tool, especially in low-resource settings. Olfactory neuroblastoma (ONB) is a rare SRBCT encountered in both pediatric and adult patients. Awareness of the cytomorphologic and immunocytochemical features of ONB is important in the workup of a SRBCT. This case report describes the primary diagnosis of metastatic ONB on FNA cytology.

Cytological diagnosis of olfactory neuroblastoma at metastatic sites, with emphasis on role of insulinoma‐associated protein 1 immunocytochemistry

“…4,5 However, these are merely suggestive, but not pathognomonic of a diagnosis of ONB, since they are also seen in other neuroendocrine and other small round cell tumors. 4,5 Mahooti et al found that identification of background neuropil along with rosettes is critical in rendering a diagnosis of ONB on aspirates. 12 However, the caveat is that this finding, although specific, is not unequivocally present in all ONB aspirates, as also seen in our study.…”

“…The cytomorphological features of ONB described in literature include high cellularity, distribution as cellular clusters and single cells, presence of nuclear moulding, paranuclear blue bodies and necrosis, and the absence of lymphoglandular bodies, amongst others 4,5 . However, these are merely suggestive, but not pathognomonic of a diagnosis of ONB, since they are also seen in other neuroendocrine and other small round cell tumors 4,5 . Mahooti et al found that identification of background neuropil along with rosettes is critical in rendering a diagnosis of ONB on aspirates 12 .…”

“…However, the description of cytological features of ONB in literature is limited, with only four case series and a few isolated reports. 4,5 Without a knowledge of the cytomorphology, recognition of ONB on FNAC at metastatic sites can be difficult, especially if relevant clinical history is not available. We recently described our experience with metastases to the parotid, which included an FNAC from a case of metastatic ONB.…”

“…The primary site of ONB is relatively inaccessible for sampling by fine needle aspiration; however, metastatic sites present opportunities for direct as well as image‐guided fine needle aspiration cytology (FNAC) diagnosis, both at presentation and later during the disease. However, the description of cytological features of ONB in literature is limited, with only four case series and a few isolated reports 4,5 . Without a knowledge of the cytomorphology, recognition of ONB on FNAC at metastatic sites can be difficult, especially if relevant clinical history is not available.…”

The current state of sinonasal malignancies and recent management updates

“…17 In another smaller case series, Penzhorn and Schubert describe the use of FNA in the evaluation of metastatic olfactory neuroblastoma and its cytologic differential diagnosis with other small round blue cell tumors, which can be addressed if adequate cell block material is available. 18 Despite the rarity of sinonasal cancers, most patients with metastatic disease detected by FNA have a known primary, which, in combination with limited ancillary studies, facilitates the cytologic interpretation of these challenging cases. 18 A major hurdle in the development of improved treatments for patients with sinonasal malignancies is that these tumors are rare, and funding for the study of such cancers is very limited.…”